Spring -- Spring Boot Mastery

Activate When

• /godmode:spring, "spring boot", "spring security"
• "spring data", "spring cloud", "actuator"
• Java/Kotlin backend work using Spring framework

Workflow

Step 1: Project Assessment

Spring Boot version: <3.3.x>
Language: Java <version> | Kotlin <version>
Build tool: Maven | Gradle (Kotlin DSL preferred)
Architecture: Monolith | Modular | Microservices
Database: PostgreSQL | MySQL | MongoDB | Redis
Auth: JWT | OAuth2 | OIDC | Session | API key

Starter selection based on requirements:

spring-boot-starter-web        REST API + Tomcat
spring-boot-starter-data-jpa   JPA + Hibernate
spring-boot-starter-security   Auth & authorization
spring-boot-starter-actuator   Health + metrics
spring-boot-starter-validation Bean validation
spring-boot-starter-cache      Caching abstraction

# Verify Spring Boot version
./gradlew dependencyInsight --dependency spring-boot
# Or Maven
./mvnw dependency:tree | grep spring-boot

Step 2: Auto-Configuration

spring:
  jpa:
    open-in-view: false        # ALWAYS disable OSIV
    hibernate.ddl-auto: validate # Flyway manages DDL
  lifecycle:
    timeout-per-shutdown-phase: 30s # graceful shutdown

IF open-in-view is true: disable immediately
  (hides N+1 queries behind lazy loading)
IF ddl-auto is create/update: switch to validate
  (Flyway/Liquibase for migrations)
WHEN deploying to K8s: enable graceful shutdown
  AND configure liveness/readiness probes

Step 3: Spring Security

SecurityFilterChain with lambda DSL:
  .csrf(csrf -> csrf.disable())  # stateless API
  .cors(withDefaults())
  .sessionManagement(STATELESS)
  .authorizeHttpRequests(auth -> auth
    .requestMatchers("/api/public/**").permitAll()
    .anyRequest().denyAll())  # deny by default

Rules:

• NEVER use deprecated WebSecurityConfigurerAdapter
• ALWAYS deny by default, explicitly permit
• BCrypt strength 12 for passwords
• Use @EnableMethodSecurity (not Global)

Step 4: Spring Data JPA

DATA LAYER PATTERNS:
  Derived queries: simple lookups by fields
  JPQL JOIN FETCH: avoid N+1 on associations
  Specifications: dynamic filtering (search)
  Projections/DTOs: lightweight reads
  @Version: optimistic locking
  Flyway: schema version control

# Generate Flyway migration
flyway -url=jdbc:postgresql://localhost/mydb migrate

# Verify no N+1 queries in logs
grep "select.*from" app.log | sort | uniq -c | sort -rn

Rules:

• ALWAYS use FetchType.LAZY for associations
• ALWAYS use JOIN FETCH when you need related data
• ALWAYS add @Version for mutable entities
• Use DTOs for API responses, never full entities
• Index every FK and every WHERE/ORDER BY field

Step 5: Actuator & Monitoring

ENDPOINTS:
  /actuator/health         Liveness probe
  /actuator/health/ready   Readiness probe
  /actuator/prometheus     Metrics scrape
  /actuator/loggers        Runtime log levels
  /actuator/env            DISABLED in prod
  /actuator/heapdump       DISABLED in prod

IF deploying to K8s: configure probes
  livenessProbe: /actuator/health/liveness
  readinessProbe: /actuator/health/readiness
  initialDelaySeconds: 30, periodSeconds: 10

Step 6: Testing

TESTING STRATEGY:
  Unit (service):     JUnit 5 + Mockito
  Controller (HTTP):  @WebMvcTest + MockMvc
  Repository (data):  @DataJpaTest + TestContainers
  Integration (full): @SpringBootTest + TestContainers
  Security:           SecurityMockMvcConfigurers
  Architecture:       ArchUnit

# Run tests with TestContainers
./gradlew test
# Or Maven
./mvnw test

Rules:

• ALWAYS use test slices over @SpringBootTest
• Use TestContainers, never H2 compatibility mode
• Use @MockitoBean (3.4+) not @MockBean

Step 7: Validation

| Check                        | Required |
|------------------------------|----------|
| OSIV disabled                | YES      |
| ddl-auto: validate           | YES      |
| Constructor injection only   | YES      |
| No entities from controllers | YES      |
| Actuator restricted in prod  | YES      |
| TestContainers for DB tests  | YES      |
| Graceful shutdown configured | YES      |

Key Behaviors

1. Convention over configuration. Override only what you need, document WHY.
2. Disable OSIV day one. Use JOIN FETCH.
3. Test slices over full context.
4. TestContainers over H2. Match prod DB.
5. Security deny-by-default.
6. Never ask to continue. Loop autonomously.

HARD RULES

1. ALWAYS set spring.jpa.open-in-view: false.
2. ALWAYS use ddl-auto: validate in production.
3. ALWAYS use constructor injection, never @Autowired.
4. NEVER return JPA entities from controllers.
5. NEVER use WebSecurityConfigurerAdapter.
6. ALWAYS use FetchType.LAZY + JOIN FETCH.
7. ALWAYS test against production DB type.
8. NEVER expose /actuator/env or /heapdump in prod.

TSV Logging

Log to .godmode/spring.tsv: timestamp\taction\tentities\tcontrollers\tmigrations\ttests_status

Quality Targets

• Target: <3s application startup time
• Target: <200ms p95 endpoint response time
• Target: >80% test coverage on service layer
• Max heap usage: <512MB for standard microservice

Output Format

SPRING: {action}. Files: {N}. Entities: {N}.
Tests: {status}. Build: {status}. Issues: {N}.

Keep/Discard Discipline

KEEP if: build passes AND tests pass
  AND no deprecated API warnings introduced
DISCARD if: build fails OR tests fail
  OR N+1 queries detected in logs

Stop Conditions

STOP when:
  - All validation checks pass
  - Build and tests green
  - Actuator secured for production
  - User requests stop